Nalon Viper

Hello John, Graham,

It looks like I may have the same bench mounted Delapena as you have John. Thing is I have never used it. I bought it off Polly Models at an exhibition quite some time ago. It was quite grotty with a damaged pulley and though near done I'm afraid it's still in a state of rebuild. I have managed to get some tooling for it but I have to say that because lapping has proved successful I've never really been motivated enough to finish it. Like wise the external hones. I was lucky enough to get two brand new sets off Ebay and though have used them still prefer to lap pistons with a home made lap

As you can see these are quickly made and do work very efficiently.

Achieving a tapered bore as Graham asks is quite easily achieved by lapping simply by dwelling at the bottom end of the liner - is this possible when honing on such a hone?

Good to hear you are making a Nalon - I look forwards to seeing your method on the bearing set up. Whilst I disagreed with your suggestion earlier it did cause me to look into bearing set up further and can see your argument from a preloaded perspective. It doesn't change my thoughts on all that has been seen before but has given rise to rethinking how preloading could be achieved without a spacer.

Graham - all the drawings are done and material now in hand.

I have another modelling project I need to finish first but hope to be starting this beginning March at latest.

Regards - Tug

This is the cylinder lap that I used as recommended by John A, Piston lap is similar to that I used Tug but will try John's suggested method with an AM25 piston this time around. Needle valve jet hole was to deep, almost 0.090 past cross holes so will make another one tomorrow.. Wish my drgs looked that good Tug, foolscap and sometimes a ruler is the best I can do LoL

Cheers

Graham W

Graham, never bothered with a tapered bore, I've always taken great care to get the bore (and piston) parallel in these small sizes. I think that the amount of taper required in these small cylinders with piston and cylinder made from the same (or very similar) metal is so small that it would be difficult to measure and I don't like the idea of guessing! I've always tried to arrange effective cooling of the cylinder to try and keep it parallel and round. Screwed on or "slip fit" fins doesn't do that.

Tug, I don't understand your point about preloading. Preloading of the bearings is to be avoided in this type of use, your design will, most definitely, preload the bearings when the engine warms up, assuming they are not when cold.

John